Each character is surrounded by an imaginary box called the
character body. The ratio of height to width in
a character body is part of the font definition. Most fonts
allow the width of the character body to vary from character to
character. For example, a capital M will be wider than a lowercase l.
Figure 8
shows the character body of a capital B.
The character body is delimited by the lines labeled left, right,
bottom, and top.
The character itself is delimited in the vertical by a base and a cap.
The distance between the base and the cap is the
character height.
The character body usually will contain some white space to the left
and right of the character in order to provide pleasing character
separations when character bodies are concatenated to produce an
output text string.

A box that consists of
the concatenated character bodies of a series
of horizontal or vertical characters defines a text extent rectangle.
Text path and alignment attributes relate to
the text extent rectangle.

Gives the direction in which a character string is to be
drawn. Options are:

0 - draw character n+l to the right of character n

1 - draw character n+1 to the left of character n

2 - draw character n+1 above character n

3 - draw character n+1 below character n

The above, below, left, and right directions are relative to the
character up vector (see routine GSCHUP).
The text path direction "right"
is perpendicular to the up vector direction. To draw a text string at
a 45 degree angle, an appropriate character up vector would be
(-1.,1.), and the text path would be right.

Normal text writing (horizontal direction moving toward the
right) defaults are a character up vector of (0.,1.) and text
path of right.

Determines the horizontal alignment of the text to be drawn.
Options are:

0 - normal

1 - left

2 - center

3 - right

TXALV

Determines the vertical alignment of the text to
be drawn. Options are:

0 - normal

1 - top

2 - cap

3 - half

4 - base

5 - bottom

Text alignment is used to indicate a position on the text extent
rectangle that will be identified with the positioning point specified
in a call to GTX. The angle of rotation at
which the text is written is determined by the character up vector
(see GSCHUP).

Figure 11, starting from the top and going down, shows the three
horizontal positions of left, center, and right combined with a
vertical alignment of "half". The next five
lines in Figure 11, going down, show the vertical alignments of top,
cap, half, base, and bottom for a horizontal alignment of center.
Normal text alignment for each text path option is given in Table 1.

Specifies the text font to be used in subsequent calls to the
GTX output primitive. Options are:

1 - Default ASCII font

-2 - Hershey cartographic Roman

-3 - Hershey cartographic Greek

-4 - Hershey simplex Roman

-5 - Hershey simplex Greek

-6 - Hershey simplex script

-7 - Hershey complex Roman

-8 - Hershey complex Greek

-9 - Hershey complex script

-10 - Hershey complex italic

-11 - Hershey complex Cyrillic

-12 - Hershey duplex Roman

-13 - Hershey triplex Roman

-14 - Hershey triplex italic

-15 - Hershey Gothic German

-16 - Hershey Gothic English

-17 - Hershey Gothic Italian

-18 - Hershey math symbols

-19 - Hershey symbol set 1

-20 - Hershey symbol set 2

The Hershey fonts are not standardized
by GKS but are locally
implemented in NCAR GKS. The Hershey font description files were
originally written by A.V. Hershey in the late 1960s and are
now made available from the National Institute of Standards
and Technology (NIST).
All of the Hershey fonts are stroked fonts,
that is, the characters are defined by a sequence of line draws.
GKS requires that locally implemented fonts be assigned negative
font numbers.

Gives the Y (vertical) world coordinate of a vector tip.
The vector tail is at (0,0). (CHUX, CHUY) cannot be (0,0).

The coordinate (CHUX, CHUY), relative to (0,0), establishes a vector
direction which will be perpendicular to the horizontal centerline
of the character string to be drawn. Thus,
(CHUX, CHUY) equals (0., 1.) implies normal character positioning
in which the character centerline is horizontal and the top of
the character is up.

Specifies a deviation of the width to height
ratio for characters drawn using the GTX output primitive.
CHXP of 10.0 would request a character that is 10 times
as wide as normal. CHXP of 0.1 would request characters
that are 1/10th as wide as normal. The character height
remains unchanged. CHXP must be greater than 0.